1. Field of the Invention
The invention relates to a light guide device, more particularly to a light guide device having improved light efficiency and uniformity.
2. Description of the Related Art
Referring to FIG. 1, a conventional light guide device 1 is shown to guide a light emitted from a light source 100 toward an optical surface 300 of a liquid crystal panel 200.
The conventional light guide device 1 includes a wedge body 11 having a light entrance side 12 proximate to the light source 100, a light reflection side 13, and a light exit side 14 opposite to the light reflection side 13. The light emitted from the light source 100 is incident upon the light entrance side 12 and enters the wedge body 11. The light reflection side 13 reflects fully the light impinging thereon back into the wedge body 11. The light exit side 14 reflects a portion of the light impinging thereon back to the light reflection side 13, and permits the other portion of the light to exit from the wedge body 11 so as to be supplied to the optical surface 300 of the liquid crystal panel 200.
In the conventional light guide device 1, the light exit side 14 is processed by etching or by forming v-cuts thereon so that a portion of the light impinging thereon can be reflected toward the light reflection side 13.
The conventional light guide device 1 can guide the light from the light source 100 toward the optical surface 300 of the liquid crystal panel 200. However, it is achieved on a basis of irregular light diffraction, in which the light efficiency is relative low on one hand, and the light distribution cannot be adjusted effectively for the light exit side 14 so as to transmit the light evenly onto the optical surface 300 of the liquid crystal panel 200 on the other hand.
Furthermore, the light used for the liquid crystal panel 200 should be one having specific polarization, such as p-type or s-type. This can be controlled by applying a polarizing coating on the light entrance side 12 or the light exit side 14. However, if the light entrance side 12 has a polarizing coating, the amount of the light entering the wedge body 11 is reduced to half of the light emitted from the light source 100. Therefore, the brightness of the light that reaches the liquid crystal panel 200 for subsequent operation will be insufficient due to light dissipation after repeated diffraction and reflection.